1. Field of the Invention
This invention relates to an interference-based exhaust noise attenuation device and method, for example to be used in conjunction with a muffler of an automobile or other vehicle.
2. Description of the Related Art
Exhaust from automobile and other internal combustion engines is extremely noisy unless muffled. This noise is largely a result of compressive waves in the exhaust flow. The conventional arrangement for attenuating the noise is a flow path configuration that includes one or more mufflers, sometimes in combination with resonators.
One problem with conventional mufflers is that they create significant backpressure that can reduce engine efficiency, power output and fuel economy. This reduction can be particularly pronounced during rapid acceleration. Modern engines rely on a certain amount of backpressure from the muffler and are designed accordingly. However, the power and efficiency of an engine are nonetheless compromised at times of greatest demand.
In addition, conventional mufflers and muffler/resonator systems bear the entire burden of attenuating noise produced by an engine. If some other simple device could significantly assist in this process, smaller, simpler, and therefore less expensive mufflers and resonators, if any, could be used.
Compressive waves in exhaust flow can also complicate the design of other exhaust system components that process the flow before the muffler. Examples of such components include but are not limited to pollution control devices and turbines.